corrupted Hydra boss

Hold Breath. The hydra can hold its breath for 5 hour.

Multiple Heads. The hydra has five heads. Whenever the hydra takes 25 damage or more on a single turn, one of its heads dies. The hydra dies if all its heads are dead. At the end of each of its turns when it has at least one living head, the hydra grows four heads for each of its heads that died since its last turn, unless it has taken fire damage since its last turn. The hydra regains 40 Hit Points when it grows new heads.

Reactive Heads. For each head the hydra has beyond one, it gets an extra Reaction that can be used only for Opportunity Attacks.

Multiattack. The hydra makes as many Bite attacks as it has heads times two.

Corrupted Bite. Melee Weapon Attack: +[Attack Bonus] to hit, reach 10 ft., one target. Hit: [Physical Damage] piercing damage plus 7 (2d6) necrotic damage.

Withered Flesh: The target must succeed on a DC [XX] Constitution saving throw or become Corrupted. While corrupted, the target cannot regain hit points until the start of the Hydra's next turn.

Forced Mutation. The Hydra spends one of its unspent Hit Dice to immediately regrow one severed head, regardless of whether it took fire damage. It gains temporary hit points equal to the roll + its Constitution modifier.

Blight Breath. (Recharge 5–6)The hydra’s heads exhale a cloud of black vapor in a 20-foot cone. Each creature in that area must make a DC 17 Constitution save, taking 24 (7d6) necrotic damage on a failed save, or half as much on a success.

The Heart of the Rot.

When the Hydra is reduced to 0 hit points, it doesn't die. Instead, its skin splits open, revealing a glowing, necrotic core. It regains 200 hit points. Additionally, its severed heads don't stop moving—they detach from the body as Corrupted Serpents (use the Giant Poisonous Snake stat block with Necrotic damage). The Hydra now has access to Mythic Actions for 1 hour.